The prior art includes devices for rotatably supporting a multiple tool holder and for rotating the holder to bring a desired tool into position adjacent a workpiece so that a machining operation can take place. One such prior art device is shown in German Auslegeschrift No. 1,293,526, wherein a generally cylindrical fixed portion of the apparatus contains an electric motor, the rotatable portion of the motor being coupled to a rotatable portion of the tool holder. This device includes a stop arrangement for preventing rotation between the fixed portion and the tool carrier whenever the motor is driven in the reverse rotational direction in order to achieve an axial movement establishing connection between driving teeth between the rotatable portion and a fixed part, the axial motion being established by axial cam surfaces. However, in this apparatus it has been found to be a significant disadvantage that when the carrier is rotated from the stop arrangement, it must travel over various stop positions. This permits only the use of weak springs which has the disadvantage of an uncertain stop support of the part to be latched by the stop arrangement.
In German Offenlegungsschrift No. 1,477,829, a manually shiftable multiple tool holder is shown wherein a locking member is axially movable.